The present invention relates to photographic color developing compositions that have improved stability, and to methods for their use. This invention is useful in the field of photography to provide color photographic images.
The basic processes for obtaining useful color images from exposed color photographic silver halide materials include several steps of photochemical processing such as color development, silver bleaching, silver halide fixing and water washing or dye image stabilizing using appropriate photochemical compositions.
Photographic color developing compositions are used to process color photographic materials such as color photographic films and papers to provide the desired dye images early in the photoprocessing method. Such compositions generally contain color developing agents, for example 4-amino-3-methyl-N-(2-methane sulfonamidoethyl)aniline, as reducing agents to react with suitable color forming couplers to form the desired dyes. U.S. Pat. No. 4,892,804 (Vincent et al.) describes conventional color developing compositions that have found considerable commercial success in the photographic industry. Other known color developing compositions are described in U.S. Pat. No. 4,876,174 (ishikawa et al.), U.S. Pat. No. 5,354,646 (Kobayashi et al.), and U.S. Pat. No. 5,660,974 (Marrese et al.).
It is generally known that the concentrations of various photochemicals used in a photographic color developing composition must be within certain narrow limits in order to provide optimal performance. This is particularly true of xe2x80x9cconcentratesxe2x80x9d or single-part compositions.
There is a trend in the photographic industry to provide photoprocessing compositions (including color developing compositions) in concentrated form so that the manufacturer and user need not pay for use, transport or storage of large volumes of water, and to enable use of smaller containers. Moreover, there has been a desire in the industry to provide compositions that can be used right out of their containers without the need for mixing various components (thereby reducing mixing errors), such as in what are known as xe2x80x9cautomatic replenishingxe2x80x9d processors.
A very useful single-part color developing composition that is homogeneous, concentrated, and stable is described and claimed in U.S. Pat. No. 6,077,651 (Darmon et al.). Such compositions are stable from the presence of the free base form of the color developing agent and a particular amount of water-soluble organic solvent.
Stability of the color developing agents in such compositions is generally achieved using sulfite ions or any of the many conventional organic antioxidants (or preservatives) that reduce aerial oxidation rates. For example, U.S. Pat. No. 4,892,804, U.S. Pat. No. 4,876,174, U.S. Pat. No. 5,354,646, and U.S. Pat. No. 5,660,974 (all noted above) describe hundreds of possible derivatives of hydroxylamines that can be used as antioxidants in color developing compositions.
The color developing compositions used in the industry are mixed with water in various parts of the world where the concentration of xe2x80x9cproblemxe2x80x9d ions such as calcium ions can vary considerably. High calcium ion content can cause precipitates that may be evident as scale or deposits on processing equipment.
To reduce the effect of such ions, color developing compositions generally contain a metal ion sequestering agent, similar to those described in Research Disclosure, publication 13410 (June 1975) and publication 20405 (April 1981). Research Disclosure is a publication of Kenneth Mason Publications Ltd., Dudley House, 12 North Street, Emsworth, Hampshire PO10 7DQ England (also available from Emsworth Design Inc., 147 West 24th Street, New York, N.Y., 10011).
Polyhydroxy compounds and aminopolyphosphonic acids are described as metal ion sequestering agents in U.S. Pat. No. 4,264,716 (Vincent et al.). Polyelectrolytes are described as calcium controlling agents in Research Disclosure, publication 22937 (May 1983). U.S. Pat. No. 6,416,940 (Haye et al.) describes the use of various polyphosphonic acids as calcium ion sequestering agents, including a mixture of such compounds with a polyacrylic acid wherein the weight ratio of polyacrylic acid to polyphosphonic acid is about 0.06:1.
Despite the description and use of various metal ion sequestering agents, there is a desire in the photoprocessing industry to find additional means for stabilizing color developing compositions, whether single-part or multi-part compositions, in the presence of calcium ions. Improved stabilization would enable any of the color developing compositions to be readily mixed with local water supplies that may be high in calcium ion content without adverse effects.
This invention addresses the problems noted above with an aqueous photographic color developing composition having a pH of from about 7 to about 13 and comprising:
a) at least 0.0005 mol/l of a color developing agent,
b) at least 0.0005 mol/l of an antioxidant for the color developing agent,
c) from about 1 to about 25 g/l of a first calcium ion sequestering agent that is a polycarboxylic acid or salt thereof having a molecular weight of from about 2000 to about 100,000, and
d) at least 0.0005 mol/l of a second calcium ion sequestering agent that is a non-polymeric aminocarboxylic acid, polyphosphonic acid, or a salt thereof,
wherein the weight ratio of the first calcium ion sequestering agent to the second calcium ion sequestering agent is from about 1:1 to about 20:1.
This invention also provides a concentrated, aqueous, single-part color developing composition having a pH of from about 8 to about 12 and comprising:
a) from about 0.005 to about 1 mol/l of a color developing agent in free base form,
b) from about 0.005 to about 1 mol/l of a hydroxyl amine derivative antioxidant for the color developing agent,
c) a water-miscible or water-soluble hydroxy-substituted, straight-chain organic solvent that has a molecular weight of from about 50 to about 200,
d) a buffering agent that is soluble in the organic solvent,
f) from about 1 to about 50 g/l of a first calcium ion sequestering agent that is a polycarboxylic acid or salt thereof having a molecular weight of from about 2000 to about 100,000, and
g) from about 0.001 to about 0.3 mol/l of a second calcium ion sequestering agent that is a non-polymeric aminocarboxylic acid, polyphosphonic acid, or a salt thereof,
wherein the weight ratio of the first calcium ion sequestering agent to the second calcium ion sequestering agent is from about 1:1 to about 15:1.
This invention also addresses the problems noted above with a two-part color developing kit comprising:
(I) a first aqueous solution having a pH of from about 9 to about 13, and
(II) a second aqueous solution having a pH of from about 3 to about 7 and comprising:
(a) at least 0.005 mol/l of a color developing agent,
(b) at least 0.005 mol/l of an antioxidant for the color developing agent, and
(b) at least 0.001 mol/l of sulfite ions,
further comprising, in the first aqueous solution, from about 1 to about 50 g/l of a first calcium ion sequestering agent that is a polycarboxylic acid or salt thereof having a molecular weight of from about 2000 to about 100,000, and in the first or second aqueous solution, or both, at least 0.0005 mol/l of a second calcium ion sequestering agent that is a non-polymeric aminocarboxylic acid, polyphosphonic acid, or a salt thereof,
wherein the weight ratio of the first calcium ion sequestering agent to the second calcium ion sequestering agent is from about 1:1 to about 20:1 when the first and second aqueous solutions are mixed at a volume ratio of from about 2:1 to about 1:2.
Still again, this invention also provides a method of making a working strength color developing composition from the two aqueous solutions noted above comprising:
(A) combining the first and second aqueous solutions noted above in such a manner that the volume ratio of the first aqueous solution to the second concentrated aqueous solution is from about 2:1 to about 1:2, and,
B) simultaneously or subsequently, diluting the first and second aqueous solutions with water in such a manner as to dilute the first concentrated aqueous solution at least 2 times and the second concentrated aqueous solution at least 2 times.
Further, this invention provides an advance in the art with a three-part color developing kit comprising:
(I) a first concentrated aqueous solution having a pH of from about 9 to about 13,
(II) a second concentrated aqueous solution having a pH of from about 1 to about 4 and comprising:
(a) at least 0.005 mol/l of a color developing agent, and
(b) at least 0.001 mol/l of sulfite ions, and
(III) a third concentrated aqueous solution having a pH of from about 10 to about 13.5,
wherein the first or second concentrated aqueous solution, or both, includes from about 1 to about 50 g/l of a first calcium ion sequestering agent that is a polycarboxylic acid or salt thereof having a molecular weight of from about 2000 to about 100,000, any of the first, second, and third concentrated aqueous solutions includes at least 0.001 mol/l of a second calcium ion sequestering agent that is a non-polymeric aminocarboxylic acid, polyphosphonic acid, or a salt thereof, and any of the first, second, and third concentrated aqueous solutions includes at least 0.005 mol/l of an antioxidant for the color developing agent,
wherein the weight ratio of the first calcium ion sequestering agent to the second calcium ion sequestering agent is from about 1:1 to about 20:1 when the first, second, and third concentrated aqueous solutions are mixed at a volume ratio of 2:1:3.
This invention also provides a method of making a working strength color developing composition from the three concentrated aqueous solutions noted above comprising:
(A) combining the first, second, and third concentrated aqueous solutions noted above in such a manner that the volume ratio of the first concentrated aqueous solution to the second concentrated aqueous solution is from about 1:1 to about 1.5:1, the volume ratio of the first concentrated aqueous solution to the third concentrated aqueous solution is from about 1:1 to about 1.5: 1, and the volume ratio of the second concentrated aqueous solution to the third concentrated aqueous solution is from about 1:1 to about 1.5:1, and,
B) simultaneously or subsequently, diluting the first, second, and third concentrated aqueous solutions with water in such a manner as to dilute the first concentrated aqueous solution at least 8 times, the second concentrated aqueous solution at least 10 times, and the third concentrated aqueous solution at least 10 times.
A method for providing a color image in a color photographic silver halide element comprises contacting the element with an aqueous photographic color developing composition having a pH of from about 7 to about 13 and comprising:
a) at least 0.0005 mol/l of a color developing agent,
b) at least 0.0005 mol/l of an antioxidant for the color developing agent,
c) from about 1 to about 25 g/l of a first calcium ion sequestering agent that is a polycarboxylic acid or salt thereof having a molecular weight of from about 2000 to about 100,000, and
d) at least 0.0005 mol/l of a second calcium ion sequestering agent that is a non-polymeric aminocarboxylic acid, polyphosphonic acid, or a salt thereof,
wherein the weight ratio of the first calcium ion sequestering agent to the second calcium ion sequestering agent is from about 1:1 to about 20:1.
The same method can also be practiced using the two and three-part color developing composition kits described above, by combining the various parts (solutions) in the kit and contacting the color photographic silver halide element with the resulting solution.
In other embodiments of the invention, a method of photographic processing comprises the steps of:
A) color developing an imagewise exposed color photographic silver halide element with a photographic color developing composition containing the first and second calcium ion sequestering agents noted above, and
B) desilvering the color developed color photographic silver halide element.
The color developing step in a photographic processing method can be followed by desilvering the color developed color photographic silver halide element, as well as any other useful photoprocessing steps known in the art.
The color developing composition is less susceptible to the formation of precipitates containing calcium ion because of the presence of two specific calcium sequestering agents. The combination of these two compounds is required to provide the desired results because each type of sequestering agent alone fails to make desired expectations. These advantages may be obtained to varying degrees with the various embodiments of the present invention.